Castable pyrotechnic colored smoke composition

ABSTRACT

A CASTABLE PYROTECHIC COMPOSITION FOR COLORED SMOKE PRODUCTION COMPRISING IODOFORM IN AN AMOUNT SUFFICIENT TO GENERATE A COLORED SMOKE, AN INORGANIC OXIDIZER IN AN AMOUNT SUFFICIENT TO OXIDE THE COMPOSITION AND A SUITABLE POLYMERIC FUEL BINDER IN AN AMOUNT SUFFICIENT TO BIND THE INGREDIENTS OF THE SMOKE PRODUCING COMPOSITION INTO A COHESIVE CASTABLE MASS.

United States Patent 3,668,026 CASTABLE PYROTECHNIC COLORED SMOKE COMPOSITION Joseph E. Flanagan, Woodland Hills, Calif, assignor to North American Rockwell Corporation No Drawing. Filed Dec. 14, 1970, Ser. No. 98,177

Int. Cl. C06d 3/00 US. Cl. 149---19 12 Claims ABSTRACT OF THE DISCLOSURE BACKGROUND OF THE INVENTION (1) Field of the invention This invention is in the field of pyrotechnic compositions for colored smoke production.

(2) Description of the prior art Colored smokes are conventionally produced either by the atomization of a dye by the use of a charge of high explosive or by volatilization of a dye by the heat produced during the burning of a pyrotechnic composition. A conventional pyrotechnic composition for colored smoke production includes a dye mixed with a heat producing composition. The heat producing composition is typically a fuel-oxidizer combination such as sulfurpotassium chlorate or sucrose-potassium chlorate. The fuel-oxidizer combination normally contains a small amount of coolant such as sodium bicarbonate.

Pyrotechnic compositions for colored smoke production are used for target identification, rescue and other forms of visual communication. A typical round of a colored smoke producing composition is a canister which is partially filled with the composition to provide a dead space above the burning charge Where the smoke can cool slightly to avoid excessive air oxidation of the heated pigment after it is discharged into the atmosphere. The charge is blended as a dry mix and pressed into the canister to give it a coherent shape. A small amount of glue or lacquer is sometimes added to help hold the pressed charge together. In some formulations a small amount of kerosene may be used to minimize dusting during processing.

To avoid the ditficulties inherent in dry pressing these pyrotechnic compositions, polymeric binders have been used to yield a castable system. However, the amount of liquid binder required is excessive when large amounts of finely divided pigment are required. Accordingly, to achieve a castable composition, the organic pigmentpyrotechnic mixture is so diluted with binder that the smoke generating capability of the charge is unacceptably reduced.

Pyrotechnic compositions for producing colored smokes have been made by incorporating an iodine-base oxidizer with a suitable fuel so that upon combustion or detonation of the composition either iodine or colored metallic iodides, or both, are formed, these materials being dispersed by the heat of the reaction. The iodine-base oxidizers which have been used are iodic acid, iodine pentoxide and heavy metal iodates including iodates of lead, silver and mercury (US. Pat. No. 3,046,168). Calcium and potassium iodates have also been used in c CO pyrotechnic compositions in combination with an oxidizer such as potassium perchlorate and a fuel such as magnesium (US. Pat. No. 2,091,977).

SUMMARY OF THE INVENTION An object of the present invention is the provision of a pyrotechnic composition for colored smoke production based on iodoform. A further object of the present invention is the provision of a castable pyrotechnic composition for colored smoke production. Other objects and advantages of the present invention will become apparent upon reading the undergoing specification and claims.

A pyrotechnic composition for colored smoke production is provided in which the composition contains iodoform in an amount sufiicient to generate a colored smoke, an inorganic oxidizer in an amount sufiicient to oxidize the composition and a suitable castable polymeric fuel binder. The inorganic oxidizer is generally an alkali metal and/ or ammonium perchlorate oxidizer optionally including an alkali metal periodate oxidizer and the castable polymeric fuel binder is preferably a polyester binder and particularly a plasticized polyester binder. The most preferred colored smoke producing composition contains, by weight, about 47 to 53 iodoform, 6 to 14% ammonium perchlorate, 6 to 14% potassium perchlorate, 0 to 12% potassium periodate, 12 to 16% polyester binder and 12 to 18% plasticizer.

DESCRIPTION OF THE PREFERRED EMBODIMENTS The castable colored smoke producing composition of the present invention is based on iodoform as the primary colored smoke producing ingredient. The composition additionally contains an inorganic oxidizer which is preferably a combination of ammonium perchlorate and potassium perchlorate optionally including potassium periodate. Finally, the composition is held together by a castable binder which additionally serves as a fuel. Virtually any polymeric binder which is compatible with the iodoform can be utilized; however, it is preferred that the binder have a relatively high oxygen content and that it cure to a rubbery state. A typical example of such a binder is the class of polyester resins. Additionally, small amounts of other materials such as fillers can be present in the composition.

The cast smoke producing composition is typically formed by mixing the ingredients together in a mixer, pouring the mix into a canister or other suitable container and curing the mix at a suitable temperature. The cast composition will generate a yellow-orange to deep violet colored smoke on burning depending primarily on the oxidizer which is employed.

The iodoform will generally vary from about 47 to 53 weight percent of the smoke producing composition. Since iodoform is normally supplied in a fine crystal or particle form, a high solids loading cannot readily be achieved in a cast composition. Accordingly, the upper limit of about 53 weight percent iodoform is dictated by the solids loading capability of cast compositions.

The organic oxidizer is generally an alkali metal and/ or ammonium perchlorate oxidizer optionally including an alkali metal periodate oxidizer and preferably a combination of ammonium perchlorate and potassium perchlorate optionally including potassium periodate. The inorganic oxidizer is used in solid particulate form in an amount varying from about 12 to 28 weight percent of the smoke producing composition. When ammonium perchlorate and potassium perchlorate are used in combination, about 6 to 14 Weight percent of each of these ingredients is employed. Potassium periodate may optionally be employed with the ammonium and potassium perchlorate oxidizers in a weight percent range of from about to 12% of composition.

In order to form a suitable castable smoke producing composition, a polymeric binder is used which additionally serves as a fuel. Virtually any binder can be used which is compatible with the iodoform. However, it is not desirable to have the smoke composition too rigid or brittle since it is often subject to shock loads particularly when used as a grenade. In fact, it is preferred that the polymer cure to a rubbery state. Additionally, it has been found desirable to use an oxygen containing binder since the quantity of solid oxidizer required can be reduced if the binder can supply some of the oxygen required for self combustion. As a result, preferred binders include the polyacrylates, polyurethanes and polyesters and particularly polyesters produced from the reaction of dibasic acids and dihydric alcohols. A typical polyester binder is hydroxy-terminated polyester resin R-18 which is supplied by Mobay Chemical Company. This hydroxy-terminated polyester resin is formed from adipic acid and diethylene glycol and has a molecular weight of about 2000.

The polymeric binder preferably contains a plasticizer and particularly a nitroplasticizer to facilitate compounding and improve flexibility. Suitable nitroplasticizers include bis-dinitropropylacrylate-formal, trimethylol ethane trinitrate and triethylene glycol dinitrate. The exact plasticizer employed will depend on the polymeric binder selected as is well known in the art.

In addition to plasticizers, the polymeric binder may contain a cross-linking agent. The preferred cross-linking agent is polymethylene polyphenylisocyanate (PAPI). Other suitable cross-linking agents which may be employed, depending upon the binder, are toluene diisocyanate, diphenylmethane diisocyanate, vinylcyclohexene dioxide and tris [l-(2-methyl)-aziridinyl] phosphine oxide.

The combination of polymeric binder, plasticizer and cross-linking agent will usually constitute from about 25 to 35 weight percent of the smoke producing composition. The weight ratio of plasticizer to hinder will generally vary from about 1:1 to 1.5: 1. The cross-linking agent will usually vary from about 5 to 25 weight percent of the polymeric binder, depending upon the materials used and the state of cure desired in the end product.

Curing catalysts such as ferric acetylacetonate (FEAA) may be added to the castable composition to provide an accelerated cure. Generally from 0.001 to 0.01 weight percent of FEAA is added to the pyrotechnic composition for this purpose. Obviously, the selection of the curing catalyst will depend on the pyrotechnic composition employed.

The pyrotechnic formulations can be made by adding iodoform, plasticizer and polymeric binder to a mixer and mixing these ingredients at a suitable temperature for a suitable period of time to achieve homogeneity. The inorganic oxidizer is then added with continued mixing. Finally, after the inorganic oxidizer has been mixed into the composition, the cross-linking agent and/or other additives such as FEAA are added and the final mix continued until all the materials have been thoroughly dispersed. The mixture is then cast into prepared hardware such as canisters or grenades or any other suitable containers for the smoke composition. Casting conditions will, of course, vary depending upon the binder and crosslinking agents utilized. As previously stated, the cure should provide a rubbery final composition as opposed to a brittle or rigid one.

An igniter is required to ignite the smoke producing composition. The smoke composition can be ignited by virtually any ignition technique utilized for solid propellant ignition. These include boron/potassium nitrate pellets, electric squibs and electric detonators. -Additionally, a first fire mix can be used. A typical ignition system is comprised of silicon, lead Oxide and cuprous oxide mixed the smoke producing with nitrocellulose in a suitable solid to form a lacquer which is spread onto the surface to be ignited.

The following non-limitive example illustrates the invention:

l EXAMPLE A gram batch of a red-orange smoke producing composition was prepared from the following ingredients:

Ingredients: Wt. percent Iodoform 51 Ammonium perchlorate 10 Potassium perchlorate 6 Mobay R-18 polyester binder 15 Triethylene glycol dinitrate 17.2 PAPI 0.8 FEAA 0.003

The ingredients were mixed in a standard air-drive A pint vertical mixer. The polyester binder and iodoform were initially added to the mixture and mixed for 15 minutes at 85 F. The mixing was then stopped and the ammonium perchlorate and potassium perchlorate were added and the mixing continued for an additional 15 minutes at 85 F. After completion of this time period the PAPI was added and the mixing was continued for an additional 5 minutes at 85 F. At this point the mixing of the pyrotechnic composition was complete and ready for casting. The composition was cast into a phenolic tube which was 4 inches long and had a diameter of 1 inch. The filled tubes were placed in an oven and cured at F. for 8 hours to a rubbery state. These filled tubes were ignited by boron/potassium nitrate pellets and provided copious quantities of red orange colored smoke.

I claim:

1. A castable colored smoke producin composition comprising iodoform in amount sufficient to generate said smoke, an inorganic oxidizer in an amount sufiicient to oxidize said composition and a polymeric fuel binder in an amount sufficient to bind the ingredients of said smoke producing composition into a cohesive castable mass.

2. The composition of claim 1 in which the inorganic oxidizer is ammonium perchlorate or an alkali metal perchlorate.

3. The composition of claim 1 in which the inorganic oxidizer is a combination of ammonium perchlorate and an alkali metal perchlorate.

4. The composition of claim 1 in which the inorganic oxidizer is a combination of ammonium perchlorate and potassium perchlorate.

5. The composition of claim 4 in which the inorganic oxidizer combination includes potassium periodate.

6. The composition of claim 1 in which the polymeric fuel binder is a polyacrylate, polyurethane or polyester binder.

7. The composition of claim 1 in which the polymeric fuel binder is a polyester resin formed from the reaction of a dibasic acid and a dihydric alcohol.

8. The composition of claim 1 in which the composition is plasticized with bis-dinitropropylacrylate-formal, trimethylol ethane trinitrate or triethylene glycol dinitrate.

9. A smoke producing composition comprising from about 47 to 53 weight percent iodoform, from about 6 to 14 weight percent ammonium perchlorate, from about 6 to 14 weight percent potassium perchlorate, from about 12 to 16 weight percent polyester fuel binder, from about 12 to 18 weight percent nitroplasticizer and from about 0 to 12 weight percent potassium periodate.

10. The composition of claim 9 in which the binder is hydroxy-terminated polyester resin formed from adipic acid and diethylene glycol and the nitroplasticizer is selected from the group consisting of bis-dinitropropylacrylate-formal, trimethylol ethane dinitrate and triethylene glycol dinitrate.

11. The composition of claim 10 in which the composition contains polymethylene polyphenylisocyanate as a cross-linking agent.

12. The composition of caim 10 in which the composition contains from about 0.001 to 0.01 weight percent 5 ferric acetylacetonate.

References Cited UNITED STATES PATENTS OTHER REFERENCES Ray Industrial and Engineering Chemistry, vol. 18, No. 1, pp. 10-18 (1926).

Feiser & Feiser, Organic Chemistry, 3rd Ed., pp. 154457, Reinhold Publishing Corporation (1956), New York.

CARL D. QUARFO'RTH, Primary Examiner 0 E. A. MILLER, Assistant Examiner U.S. C1. X.R. 149-20, 76, 78, 84 

